Tom and Clive --
Thanks for the info. Fortuitous that you should happen to have mailed me that
info today as I spent most of the day stripping down the intake vaccuum
system, which also gives me (rare) access to the throttle valve unit and connector.
To stick with this topic for a second, I tested the throttle resistance today
and didn't notice any appreciable 'dips'. However, I'd agree with Tom that
the meter may not respond quickly enough to catch any of the dips for this
particular problem. I've noticed that my multimeter takes a second or so to
respond, and that's generally the duration of the dip. Maybe it's because I've got a
relatively cheap consumer digital multimeter and that pro ones give you a
faster response. However, the immediate thing that I need to ask the list, quite
urgently as I have to put the intake air plenum back on tomorrow, is this: when
I unplugged the connector to the throttle valve unit, I was surprised, in
that on the throttle pot connector itself (the one actually on the throttle pot)
is a six-pin connector. All well and good. However, on the connector to the
engine control unit, contact 5 is missing. I just need to ask whether this is
normal, or whether one of my contacts has pushed itself back into the holder! I
do find it odd that you'd have a six pin connector and then just not have one
pin in the middle of the corresponding connector... I mean since it was
designed for that ignition system, why not just have a 5 pin connector and be done
with it?! Could anyone tell me, fairly urgently whether this is normal or not?
The connector is fairly innacessable, so I'd rather not try to pull back the
rubber grommet unless I have to, to check whether there's a stray contact
inside!
Obviously, if the contact IS supposed to be there, this could be the cause of
my problems!
Tom, the contacts look shiny and clean, but I'll give 'em a good spray of
Deoxit and plug/unplug them a few times to make sure. Your theory of the contact
'bouncing' makes sense and what you describe about this 'confusing' the ECU
seems to describe what happens in that the car stays at the same revs, as though
the ECU is thinking 'uh... so... what do you want me to do, exactly?' until
it gets new 'clean' information by you either pressing further on the throttle
to a 'clean' area, backing off the throttle again to a non-broken part, or
until it gets wiped clean.
A second (and third) question regards the vaccuum system. Has anyone else
found that their vaccuum system doesn't correspond to the system in the manual?
Mine has quite notable differences:
a) I can't see a vaccuum connection to the brake servo (in fact, now I'm
looking for it, I can't see anything resembling a brake servo on this car (yet the
brakes work fine).
b) It looks like I'm missing at least one 'non-return valve' just next to the
fuel pressure regulator. I just have one next to the intake manifold
changeover valve.
c) The non-return valve I do have doesn't seem to work in either direction
(at least not with the amount of pressure I can generate with my lungs to blow
into it)
d) On the intake manifold changeover solenoid valve (electric, not the
vaccuum operated valve) there are two plastic vaccum hose connections and then a
metal 'connection' coming out of the front. This metal connector is 'plugged' by
a plastic plug, but when I blow into the valve from one of the other
connectors, this plug doesn't seal the connector. I pulled it off and it's designed
with slits cut down the inside so that it delibarately doesn't seal this
connector, but is this an original plug designed this way, or should this connector be
sealed tight?
I know that's a lot of questions, but mainly I'm asking 'how do these things
look on your car' because I don't have another V6 locally to compare, and the
Audi diagrams don't describe the system on my car completely accurately!
Thanks guys
James
In a message dated 27/3/04 5:25:54 am, tomchr at ee.washington.edu writes:
In the past I have checked the sensor the following way although I am not
sure of AUDI config
1 pin is ground
1 pin is =5 volts
1 pin = signal out
you should be able to put a voltmeter on signal out and ground and watch the
voltage change as you change the throttle position. you should have a steady
increase in voltage up to about 5 volts , which is "flood" condition to the
ecu with no drop outs of voltage. If you slowly open it and find the voltage
drops off at somepoint you have found your problem. I think Tom may have a bently
with the info you need.
> Eh... I guess that should have been pin 1, 2, 3...
>> >you should be able to put a voltmeter on signal out and ground and watch
> >the voltage change as you change the throttle position. you should have a
> >steady increase in voltage up to about 5 volts , which is "flood"
> >condition to the ecu with no drop outs of voltage. If you slowly open it
> >and find the voltage drops off at somepoint you have found your problem. I
> >think Tom may have a bently with the info you need.
>> You may not catch any discontinuities with a voltmeter or ohmmeter. The
> sampling time of the meter (and the response of your eyes) isn't fast
> enough. What typically happens as the pot wears is that the wiper will
> 'bounce' on the resistive track. The bouncing happens pretty fast and won't
> necessarily show up on your meter. But it will confuse the ECU.
>> James: Before buying a new throttle pot, check the connector. Give it a
> good cleaning with contact cleaner.
>> Tom